The present invention relates to the art of electrical potential determination. It finds particular application in determining true or absolute potential and measuring other potentials on an absolute scale. It is to be appreciated that the present invention is applicable to monitoring the potential and change in potential relative to an absolute scale. The potential of earth ground or other objects such as aircraft, fluid or grain containers, chemical reaction tanks, hospital patients, and the like may be measured.
The present state of the art of potential measurement consists of the comparison of two potential sources by observing the voltage difference between them and assuming that one of them is of either an arbitarily assigned zero or non-zero value. This provides knowledge of a gradient or voltage difference without knowledge of the true or absolute potential of either source. Earth ground is often considered as reference zero for convenience, a convention that dates back to the earliest days of electrical science. Mathematically, electrical potential is defined as the work required to bring a unit of charge from infinity to the location of that potential without disturbing its value. Although infinity is defined as zero potential, the earth is considered a more convenient local zero potential reference by common convention. It can be shown, however, that the absolute potential of the earth is not zero.
Instruments located on an aircraft or other objects that are isolated from the earth are commonly "grounded" to the isolated object. An aircraft, however, tends to assume the potential of the surrounding atmosphere. Although the isolated object is assigned the zero potential value, it is frequently at a different potential relative to the earth. For example, in fair weather, an aircraft at cruising altitude may have a potential that is 100,000 volts different from that of the earth surface. If the aircraft passes through a charged cloud of a severe thunderstorm, the potential of the aircraft and its occupants may experience a change in potential of 100,000,000 volts in a few seconds or minutes.
Aircraft in flight experience different aerodynamic forces due to friction changes when the potential of the aircraft surface changes. Large potential changes may contribute significantly to wind shear phenomenon. A detection system responsive to electrostatic potential and its change may warn of impending wind shear and compensate for such sudden occurences. The devices presently in use to measure space charge gradient will not provide the same information.
Many costly accidents happen each year involving the transfer and storage of explosive and flammable gases and liquids. Electrical sparks may trigger explosions during transfer and handling of explosive fluids and powders, such as in grain storage silos, in coal mining, during mid-air refueling, during tank cleaning, and the like. Electrical sparks can also cause flash fires in hyperbaric oxygen chambers, during tanker docking, and the like. The knowledge of true static charge distribution can be a significant aid to the reduction in loss of life and property and the development of safety practices.
The potential of the earth is not constant. Rather, it varies with time, location, and natural phenomena. Heretofore, observations have been made of electrical current flow through the earth and its atmosphere. These telluric current flows manifest themselves in transmission problems across long distance telegraph and telephone lines, particularly lines which extend through regions of the earth that are at significantly different potentials. These earth currents, of course, would not exist if the earth had a uniform and constant potential.
Since the eighteenth century, observations of atmospheric electricity, thunderstorms, the aurora, and fair weather vertical gradient, have shown us that there is a considerable variation with time and location, in the relative potential of the atmosphere, clouds, and earth surface. Today, it is generally accepted that the surface of the earth is some four hundred thousand volts negative in comparison to the electrosphere, located fifty thousand meters above. Lightning proves that charge concentrations of millions of volts potential can be found within the atmosphere. Swarms of energetic charged particles shower the earth from the solar corona and from beyond our solar system, suggesting that the potential of the earth may be changing with the tides, weather patterns, magnetic storms, seasons, and solar cycles.
It has been suspected that such potential changes influence agriculture, health, transportation, industry, and the like. However, the convention of referencing earth ground potential as zero has obscured correlations between electrical potential changes and observed phenomena.
There are a variety of industrial processes which seem to suffer from "full moon" type effects. From the rate of build-up of boiler scale, to the rate of polymerization of colloidal systems, there is something going on which has not yet been identified. It may be solar wind in a twenty eight day cycle mimicking that of the moon. Bleeding rate during surgery, migraine onset, and neurological disorders show cyclic data patterns which sometimes, but not always, follow a lunar pattern.
Studies have been undertaken linking weak slowly changing magnetic fields with biological and physiological activity. No satisfactory connecting or causal link has been established as a mechanism for this to happen. There is a link between change in pH activity and many of these types of effects. pH represents a form of charge concentration or distribution which is often static in nature. A knowledge of absolute potential and its slow changes with time may explain these effects.
The present invention provides an apparatus and method for determining variations in potential which are comparable with potential measurements made at times or places with a different ground potential.